The provision of a multi-use vehicle adapted for travel both over ice and water presents a combination of problems. Two principal problems are the support of the vehicle, on both media, and the propulsion of the vehicle on both media. In a typical situation, such a vehicle may be travelling over ice, around the shoreline of a body of water, and at some point there will be a transition to water, and then the vehicle may again be travelling over ice. The vehicle must be capable of making such a transition smoothly, and without any warning, since it is often difficult to determine exactly where the transition will take place. Thus, both the support of the vehicle and its propulsion means must be fully suitable to travelling on both media one after the other, and to making the transition from one media to the other at any moment.
Clearly, since the vehicle is to be travelling at least in part over water, then there must be some means of buoyancy provided, in the form of some form of hull. However, typical marine hulls do not lend themselves in any way to travel on ice. In the selection of a means of propulsion, it is apparent that the typical marine propeller type of propulsion means used in water will be inoperative on ice. On the other hand, traction belt propulsion devices such as are used in snow vehicles, which are suitable for travel over snow and ice, are unsuitable for propulsion in water. In the past, proposals have been made for multi-media vehicle known as "all terrain vehicles" (ATV) which were provided with a water proof body, and a set of four or six oversized, low pressure tires. These vehicles did have a relatively limited capability of travel on ice, although with very little real control, and also a limited degree of capability for travel in water, at low speeds. However, generally speaking, they were not suitable for travel in snow and, in fact, ATVs find their greatest application on land "off road". Ground effect vehicles are known, in which a large fan is provided, driving air downwardly so that the vehicle in fact rests on a cushion of air. These vehicles will perform on almost any surface, and would certainly perform on intermittent patches of water and ice, and on snow. However, they are relatively expensive to manufacture and are inefficient to operate.
One of the uses for which the present invention is particularly suited is the rescue of persons who become marooned on moving ice floes. This situation occurs every year, when ice fishermen remain on the ice too late in the season. Attempts to rescue them using a conventional boat can be frustrating, at the least, and also dangerous. These situations may occur on lakes in widely scattered areas, and it is desirable that a rescue craft shall be available which can be placed on a trailer, and rapidly transported to the scene, and this is simply impractical with ground effect air-cushion vehicles.
It will, of course, be appreciated however that the invention may have numerous other applications besides simply the rescuing of persons on ice floes, and the invention is not to be considered as in any way restricted to this situation.
Marine craft are known for travelling in shallow water, or in swampy areas, which consist typically of pontoons, and a propulsion unit consisting of an engine driving an aircraft propeller. These craft are excellent for the purpose for which they are intended. However, they would not be in any way suitable for making a transition from water to ice and back again.
These pontoon swamp craft are typically used at a permanent location, by commercial operators, providing transportation to the public on a fare-paying basis, for example, in wildlife swamps in sub-tropical locations.
Typically these craft will be built to order, and in fact have not enjoyed wide distribution. From an economic viewpoint, it is clearly desirable to provide a multi-media craft which is both useful, and also provides an enjoyable sport for persons interested in outdoor activities in the winter. The success of the track-driven snow vehicle industry is clear evidence that there is a major market in this area. However, in order to reap the potential of the market for a multi-media vehicle capable of travelling on water and ice, as well as snow, it is necessary to have a vehicle which can be manufactured on a mass production basis, and which ideally is capable of being shipped in a knocked-down condition as a kit, and which can then simply be assembled by the consumer, or the distributor, as the case may be.